In a conventional two-axis, dynamically tuned gyro the rotor is connected to the drive shaft of the motor through a gimbal, which is connected on one hand to the drive shaft and on the other hand to the rotor through spring joints. With deflection of the gyro housing relative to the gyro rotor the spring joints would normally exert a torque on the gyro rotor, which causes this rotor to change its reference attitude in space. In a dynamically tuned gyro the tuning is selected such that the torques caused by the spring joints are compensated by dynamic torques. These dynamic torques are caused by an oscillating motion of the gimbal which occurs when the gyro housing is deflected relative to the space-fixed gyro rotor.
In such dynamically tuned gyro it is known to provide two or more concentrically arranged gimbals (U.S. Pat. No. 3,678,764). With appropriate selection of the moments of inertia of the gimbals errors may be eliminated which occur due to a "rectifier effect" with external vibrations at twice the gyro rotary speed. The gyro of U.S. Pat. No. 3,678,764 requires hight precision and thus high manufacturing expenditure.
By German Pat. No. 2,429,913 a gyro assembly with dynamically tuned gimbal suspension of the rotor on the drive shaft is known, in which the gimbal suspension comprises three gimbals, each of which is connected with the rotor and the shaft through flexural pivots angularly offset by 90.degree.. The corresponding flexural pivots of different gimbals are offset by 120.degree.. Gimbals are formed of cylindrical gimbal rings. They are connected with the rotor and the driving shaft through pairs of diametrically opposite flexural pivots. The gimbals are arranged concentrically one within the other. Also this construction is made of many individual parts and therefore expensive.
Furthermore cardan joints with spring elements are known, in which the spring elements are heavily restricted bending rods (German Pat. Nos. 1,281,216, 1,947,893 and 2,150,604). In these bending rods the range which may be deformed is reduced to a minimum. This causes high material tensions in the marginal zones, when the rod is deflected.
U.S. Pat. No. 3,700,290 discloses a dynamically tuned gimbal suspension for supporting a gyro rotor with two degrees of freedom comprising first and second generally hollow-cylindrical rings. The second ring is arranged coaxially to the first ring. Each of the rings has two pairs of axially spaced generally peripheral cuts. Each pair of cuts of the first ring defines, therebetween, a pair of diametrically opposite axially extending bending springs. The bending springs defined by one of the pairs of cuts are angularly spaced by 90.degree. from the bending springs defined by the other pair of cuts. In similar manner, each pair of cuts of the second ring defines, therebetween, a pair of diametrically opposite, peripherally extending bending springs. Again the bending springs defined by one of the pairs of cuts are angularly spaced by 90.degree. from the bending springs defined by the other pair of cuts. Thus the cuts divide the first and second rings into three ring portions each, which are flexibly interconnected by bending springs. The ring portions of the first and second rings are interconnected such that the peripheral and axial bending springs form flexural pivots. The median ring portions form gimbals. The end portions of the rings are interconnected and connected to the gyro rotor and to driving means, respectively.
The cuts in this gimbal suspension are very unsymmetrical and comprise a combination of both cuts proper and circular bores. This makes manufacturing complex and costly.
In addition the bending springs of U.S. Pat. No. 3,700,290 are defined by the circular bores and therefore buckle substantially about a single point, namely the point of the heaviest restriction. This causes high material stresses in the marginal zones when deflection occurs.